More than 100 members of Congress expressed their "firm opposition" to a proposal by MLB that would eliminate more than 40 minor league teams.
The letter, signed Tuesday and addressed to commissioner Rob Manfred, warned that the proposal would "devastate our communities, their bond purchasers and other stakeholders affected by the potential loss of these clubs."
The current agreement between Major League Baseball and the minor league teams -- called the Professional Baseball Agreement -- expires at the end of the 2020 season.
MLB is looking to make some major changes that would overhaul all levels of the minors, particularly at low Class A and below.
According to one proposal by MLB, the more than 40 teams at the lower levels that are not included in this venture would be reclassified into a "Dream League," which would be run jointly by MLB and Minor League Baseball and would include players who were not selected in the draft.
"Reducing the number of Minor League Baseball clubs and overhauling a century-old system that has been consistently safeguarded by Congress is not in the best interest of the overall game of baseball, especially when Major League Baseball's revenues are at all-time highs," the letter said.
MLB deputy commissioner Daniel Halem issued a lengthy response to the letter on Tuesday which said the proposed changes align with MLB's attempt to improve player travel and working conditions.
"... we have identified more than 40 Minor League stadiums that do not possess adequate training facilities, medical facilities, locker rooms, and, in some cases, playing fields, to satisfy the requirements of our Clubs and players," MLB's response read. "MiLB has communicated to us that it is unrealistic for us to expect lower-level Minor League affiliates to meet our facility standards because of the costs involved in upgrading the facilities."
The response also said MLB is looking to improve player compensation heading into the new agreement.
Currently, MLB pays the entirety of minor league salaries, and players at Class A affiliates receive as little as $1,160 per month; those in their first season at Triple-A make just $2,150 a month before dues and taxes.
Minor league players are legally unable to earn overtime after Congress inserted a cutout into a $1.3 billion spending bill last spring that exempted teams from paying beyond the $7.25 minimum wage at 40 hours a week.
Of the Congress members who signed the letter Tuesday, 54 voted in favor of that spending bill. There were fewer who voted no on the bill, and several who were not in Congress in 2018.
ESPN's Jeff Passan contributed to this report.